1. Field
Embodiments of the present invention relate to a pedal simulator, and more particularly, to a pedal simulator for an active brake system, which may enhance pedal feeling.
2. Description of the Related Art
Generally, an active brake system is a brake system in which, when a driver presses his/her foot down on a brake pedal, an electronic control unit (ECU) detects this state, drives a hydraulic pressure generating unit, and supplies a hydraulic pressure to a master cylinder, and thus a braking hydraulic pressure is transmitted to a wheel cylinder of each wheel, and a braking force is generated. In this active hydraulic control booster, a pedal displacement sensor detects a displacement of the brake pedal in a normal brake state, when the driver presses his/her foot down on the brake pedal. The ECU operates the hydraulic pressure generating unit, and controls a hydraulic fluid stored in a hydraulic fluid storage to be supplied to a boost chamber of the master cylinder, such that a pressure is formed in the master cylinder. The pressure formed in the master cylinder presses a piston of the master cylinder, thereby generating a braking hydraulic pressure. The braking hydraulic pressure is transmitted to the wheel cylinder, and generates a braking force.
At this time, if the pressure of the master cylinder is changed upon a regeneration braking, force corresponding to the pressure change is directly transmitted to the brake pedal and thus has a bad influence on pedal feeling. When the pedal feeling is deteriorated, there is a gap between the pedal feeling felt by the driver upon a braking operation and an actual pressing degree of a brake disk of a brake pad in the wheel cylinder, and thus the braking operation is excessively or insufficiently performed, and consumable components such as the brake pad should be frequently replaced, and it may have great influence on a safety accident of a vehicle, such as sudden braking and insufficient braking.
Therefore, conventionally, a pedal simulator is used at the active brake system to provide a reaction force to the brake pedal. As disclosed in Korean Patent No. 10-0657576, two springs as damping members are used in the pedal simulator to provide the reaction force according to a brake pedal force, and thus a simulator piston is damped. However, as illustrated in FIG. 1, since the two springs provide brake pedal feeling in only a simple primary linear type, desirable brake pedal feeling may not be provided.
Further, in a structure in which the two springs are arranged in series, when the reaction force is provided through a first spring in an initial low pedal force section and the piston is operated according to an installation load of the first spring, bump feeling is generated and thus the pedal feeling is deteriorated.